diff --git a/components/style/properties/data.py b/components/style/properties/data.py
index 8f3c7d35269..b2ab520ad3d 100644
--- a/components/style/properties/data.py
+++ b/components/style/properties/data.py
@@ -340,13 +340,14 @@ class Longhand(Property):
         assert (
             has_effect_on_gecko_scrollbars in [None, False, True]
             and not style_struct.inherited
-            or (gecko_pref is None) == (has_effect_on_gecko_scrollbars is None)
+            or (gecko_pref is None and enabled_in != "")
+            == (has_effect_on_gecko_scrollbars is None)
         ), (
             "Property "
             + name
             + ": has_effect_on_gecko_scrollbars must be "
             + "specified, and must have a value of True or False, iff a "
-            + "property is inherited and is behind a Gecko pref"
+            + "property is inherited and is behind a Gecko pref or internal"
         )
         self.need_index = need_index
         self.gecko_ffi_name = gecko_ffi_name or "m" + self.camel_case
diff --git a/components/style/properties/longhands/font.mako.rs b/components/style/properties/longhands/font.mako.rs
index e84a5574d1a..f5304355e03 100644
--- a/components/style/properties/longhands/font.mako.rs
+++ b/components/style/properties/longhands/font.mako.rs
@@ -213,6 +213,7 @@ ${helpers.predefined_type(
     initial_value="computed::XLang::get_initial_value()",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     spec="Internal (not web-exposed)",
 )}
 
@@ -224,6 +225,7 @@ ${helpers.predefined_type(
     animation_value_type="none",
     gecko_ffi_name="mScriptSizeMultiplier",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     spec="Internal (not web-exposed)",
 )}
 
@@ -263,6 +265,7 @@ ${helpers.single_keyword(
     spec="Internal (not web-exposed)",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     needs_conversion=True,
 )}
 
@@ -273,6 +276,7 @@ ${helpers.predefined_type(
     engines="gecko",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     gecko_ffi_name="mScriptMinSize",
     spec="Internal (not web-exposed)",
 )}
@@ -284,6 +288,7 @@ ${helpers.predefined_type(
     engines="gecko",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     spec="Internal (not web-exposed)",
 )}